1. Field of the Invention
The present invention relates to a radiation sensitive resin composition and, more particularly, to a positive-tone or negative-tone radiation sensitive resin composition which allows easy preparation of a resist, exhibits superior storage stability, high sensitivity, and high resolution capability, and is capable of producing excellent resist patterns.
2. Description of the Background Art
There is an increasing demand for miniaturization, requiring reduced processing sizes in lithography, in fields requiring fine work such as manufacture of integrated circuits (ICs) in order to achieve high integrity in ICs. Technologies capable of fine processing, even of a size of 0.5 .mu.m or smaller, in a stable manner have become necessary in recent years. Because of this, resists used in such a technology must be capable of forming patterns smaller than 0.5 .mu.m at high precision. It is extremely difficult to produce a minute pattern smaller than 0.5 .mu.m at a high precision by conventional methods using visible light (wavelength 800-400 nm) or near ultraviolet light (wavelength 400-300 nm). Because of this, the use of short wavelength radiation (wavelength 300 nm or less) has been studied.
Given as examples of such a short wavelength radiation are deep ultraviolet rays, such as a bright line spectrum of a mercury lamp (wavelength 254 nm), a KrF excimer laser (wavelength 248 nm), and an ArF excimer laser (wavelength 193 nm); X-rays such as synchrotron radiation; and charged particle rays such as an electron beam. Of these, lithography using an excimer laser is attracting a great attention due to its high output and high efficiency. For this reason, the resists used in lithography also must produce minute patterns of 0.5 .mu.m or less with high sensitivity and high resolution by excimer laser with good reproducibility.
Chemically amplified resists using a radiation sensitive acid generator which generates an acid by being exposed to radiation (hereinafter referred to as "exposure") and in which the sensitivity of resist is increased by the catalytic action of the acid has been proposed as a resist applicable for use with deep ultraviolet light such as from an excimer laser.
As examples of such chemically amplified resists, a combination of a resin protected by a t-butyl group or t-butoxy carbonyl group and a photoacid generator is disclosed in Japanese Patent Application Laid-open No. 45439/1984. Japanese Patent Application Laid-open No. 52845/1985 discloses a combination of a resin protected by a silyl group and a photoacid generator. Beside these, there are many reports relating to chemically amplified resists such as, for example, a resist which contains a resin having an acetal group and a photoacid generator (Japanese Patent Application Laid-open No. 25850/1990).
In these chemically amplified resists, an onium salt such as, for example, triphenylsulfonium trifluoromethanesulfonate is used as the photoacid generator. However, onium salts require careful quality control in the preparation of resists because the onium salts are scarcely soluble in the solvents used for the resists. Other compounds such as a sulfonic acid ester of 2,6-dinitrobenzyl and tris(methanesulfonyloxy) benzene, and bis(cyclohexylsulfonyl) diazomethane are not suitable as the photosensitive component for a chemically amplified resist due to their poor sensitivity.
Accordingly, development of a photoacid generator capable of providing superior resist performance, such as high resolution and highly sensitivity, and exhibiting high solution capability in the solvents used with the resists is strongly desired.
In view of these problems in conventional technologies, an object of the present invention is to provide a positive-tone or negative-tone radiation sensitive resin composition allowing easy preparation of a resist, exhibiting superior storage stability, high sensitivity, and high resolution capability, and capable of producing excellent resist patterns, by selecting a photoacid generator which is highly sensitive to light, especially to deep ultraviolet rays, generating an acid at a high efficiency by being exposed to low level radiation and is abundantly soluble in solvents used with the resist.